The Northridge Earthquake: January 17th, 1994

  • andreduce

    Posts: 76

    Jan 17, 2016 10:12 PM GMT
    At 4:31 am, January 17th, 1994, the San Fernando Valley in southern California was struck by a 6.7 magnitude earthquake that lasted up to 20 seconds. What came to be known as the Northridge earthquake (named for the northern LA neighborhood almost directly above its epicenter) claimed 57 lives. Sixteen of those who perished were sound asleep their beds on the first floor of the Northridge Meadows apartment complex when the rest of the building crushed the entire ground floor. Officer Clarence Wayne Dean was riding his motorcycle toward the Newhall Pass Interchange in the dark when he tragically careened to his death due to not seeing the collapsed section of freeway. One year later, the Interchange was renamed in his honor.
    As a result of Northridge, several building codes were updated. One relatively substantial code revision was not allowing 'soft' first floors where there is a whole extra space for parking below the building. This prevents upper floors from giving way and landing on the cars below.
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    Jan 17, 2016 10:28 PM GMT
    I remember that one! That was probably the biggest earthquake I remember being in, in the 20ish years I lived in SoCal.
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    Jan 17, 2016 11:46 PM GMT
    andreduce saidAs a result of Northridge, several building codes were updated. One relatively substantial code revision was not allowing 'soft' first floors where there is a whole extra space for parking below the building. This prevents upper floors from giving way and landing on the cars below.

    Hey, it's LA; gotta protect those cars!
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    Jan 17, 2016 11:53 PM GMT
    For a long time I thought the magnitude of an earthquake was how strong the shock was; i.e., if it was high intensity in a short period of time. But a long drawn out one can easily be a higher magnitude.

     Magnitude is a measure of the amount of energy released during an earthquake. It may be expressed using several magnitude scales. One of these, Used in Southern California, is called the Richter scale.
  • andreduce

    Posts: 76

    Jan 18, 2016 12:05 AM GMT
    Lumpyoatmeal saidFor a long time I thought the magnitude of an earthquake was how strong the shock was; i.e., if it was high intensity in a short period of time. But a long drawn out one can easily be a higher magnitude.

     Magnitude is a measure of the amount of energy released during an earthquake. It may be expressed using several magnitude scales. One of these, Used in Southern California, is called the Richter scale.


    yeah that makes sense. Earthquakes are not my forte (that honor goes to stroms in the great plains for me) but it would seems the longer a quake, the more violent it is or at least can be, logically.
  • bro4bro

    Posts: 1035

    Jan 18, 2016 4:24 AM GMT
    andreduce said
    Lumpyoatmeal saidFor a long time I thought the magnitude of an earthquake was how strong the shock was; i.e., if it was high intensity in a short period of time. But a long drawn out one can easily be a higher magnitude.

     Magnitude is a measure of the amount of energy released during an earthquake. It may be expressed using several magnitude scales. One of these, Used in Southern California, is called the Richter scale.


    yeah that makes sense. Earthquakes are not my forte (that honor goes to stroms in the great plains for me) but it would seems the longer a quake, the more violent it is or at least can be, logically.


    OK guys, listen up - I used to work as a seismologist.

    All earthquakes start their lives as a single impulse - a "pop". more or less, created when pressure builds up to the extent that the earth buckles. But seismic energy travels through the earth in various wave modes, each with their own characteristic speed (which depends on the type of rock they're traveling through).

    So, as you move farther and farther away from the epicenter, the different waves (which started out together) arrive at different times. What started as a single pop becomes a long rumble.

    If an earthquake feels like a sharp, brief shake, you're probably very near the epicenter. If it feels like a long rolling rumble, you're probably far away. In either case, a higher magnitude quake will feel stronger than a lower magnitude quake. But a 4.0 that you're sitting right on top of may feel a lot stronger to you than a 6.0 that's 50 miles away.

    I'm oversimplifying a bit; there are other effects such as frequency dispersion, reflections, liquefaction of soil, etc that can have a big impact on what you feel. But basically earthquakes can be thought of much like thunder and lightning - if lightning strikes right next door, you hear a sharp crack; if it strikes far away, you hear a long low rumble.

    Oh, and NOBODY can accurately predict when or where an earthquake will occur.
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    Jan 18, 2016 5:39 AM GMT
    bro4bro said
    Oh, and NOBODY can accurately predict when or where an earthquake will occur.

    Didn't an Italian court convict some seismologists a few years ago, because they hadn't predicted a deadly quake? I believe the scientists were eventually exonerated after a series of appeals.
  • bro4bro

    Posts: 1035

    Jan 19, 2016 5:00 AM GMT
    Yes, after the 2009 quake in L'Aqila that killed something like 300 people. The seismologists were found guilty of manslaughter for not warning people an earthquake was coming. This is like convicting a weatherman for not warning the public about an impending tornado. Thankfully, they were acquitted in an appeal.

    It doesn't speak well for the Italian legal system, does it? Well, after all, they threw Galileo in prison too.

    There was an incident in L.A. 25 or so years ago that I thought was just as ridiculous. A Spanish language newspaper in town (NOT a sensationalistic tabloid) printed a story that a major earthquake was going to hit within a month, based on the word of a psychic. The Seismological Lab at Caltech was livid. They demanded to know how the story could have been published.

    The paper's answer: "Well, we asked you when the next earthquake would be and you said you didn't know. But the psychic said he knew, so we printed his story."

    In geological time, a hundred years isn't even the blink of an eye. Predicting the day, the month, or even the year an earthquake will happen is like chopping away at a redwood tree - you know it's coming down sometime - and predicting the exact moment it will topple, to the millisecond.
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    Jan 19, 2016 5:05 AM GMT
    bro4bro saidIt doesn't speak well for the Italian legal system, does it?

    Beats convicting some Mafia guy; the Mafia guys hire a hit man to go after the judges and shoot them. Seismologists aren't likely to do that.
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    Jan 19, 2016 7:22 PM GMT
    Lumpyoatmeal said
    bro4bro saidIt doesn't speak well for the Italian legal system, does it?

    Beats convicting some Mafia guy; the Mafia guys hire a hit man to go after the judges and shoot them. Seismologists aren't likely to do that.


    But you've never met CalTech's seismidyke, have you?
  • bro4bro

    Posts: 1035

    Jan 19, 2016 8:16 PM GMT
    I guess you're referring to Dr. Lucy Jones. Yep she's an imposing figure all right.

    She's also married (to a man) and has two sons.
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